Preservation of rubber



Patented Nov. 28, 1939 UNITED STATES ATEN'T QFiQE Manchester,

Great Britain England, assignors to Imperial Chemical IndustriesLimited, a

corporation of No Drawing. Original application May 21, 1936,

Serial No. 81,124. tion February 2,

Divided and this applica- 1937, Serial No. 123,601.

Great Britain May 24, 1935 8 Claims.

This invention relates to the preservation of rubber.

It is well known to those engaged in the manufacture of rubber articlesthat rubber, even after vulcanization, deteriorates with the passage or"time, with exposure to air and light, and under the influence of otheragencies and Circumstances. This processof deterioration believed to beat least in part one of oxidation, because it can be greatly acceleratedby oxygen. To reduce this deterioration, substances known asantioxidants or antiagers have been added to the rubber, and their usehas become an established industrial practice. These antioxidants areusually organic chemical compounds. These compounds, whether or notcolored themselves, frequently cause discoloration of the rubberarticle, either during compounding, vulcanizing or subsequent exposure.This discoloration is commonly spoken of as staining. While staining isnot a disadvantage in making many rubber articles, such as for exampletyre treads it is a disadvantage in some, particularly where a white orpale colored rubber article is required, as in certain floor coveringmaterialsand wearing apparel. Hitherto, the antioxidants, which havebeen most effective in preventing deterioration have also causedstaining, and conversely those which have been satisfactory or nearlysatisfactory as regards non-staining have fallen short in preventingdeterioration.

viding compounds obtainable by interacting equimolecular proportions ofa xylenol, formaldehyde and a member of the class consisting ofpiperidines, morpholines and dialkylamines in which each alkyl groupcontains 1 to .1 carbon atoms. By the term piperidlnes and morpholinesas employed herein and in the claims, We mean piperidine, morpholine andtheir homologues, such as for example, pipecolines,'lupetidin-es,aethyl-piperidine, a-propyl-piperidine, tetrahy-- drcquinoline andtetrahydroquinalidine and the like in which the sole substituents arehydrocarbons. By the term a xylenol as employed herein and in theclaims, we mean any of the isomeric xylenols. However, for our purpose,the compounds prepared from the 1:3:2-xylenol are the most desirable andare the preferred compounds.

The compounds of our invention may be made by reacting one mole offormaldehyde with one mole of piperidine, morpholine or dialkylamine andthen reacting the resulting product with one mole of xylenol. We havefound that the resulting products, when incorporated in rubber by any ofthe methods ordinarily employed in practice, confer on the rubber highresistance to aging without staining it or staining it more thanslightly.

Our invention is illustrated by the following table, which shows theresults of tests carried out on vulcanized rubber with 5 of thecompounds.

Tensile strength in kg/sq. cm. A t d t Staining iafter1 ex 11 ioxi anposure o u tra- Before 3%; ff violet light ageing Y g y mg ageing5-piperidinomethyl-l13:2-xylenol (M. P. ll9120 O.) 173 161 137 Similarto blank. S-dimethylamino-methyl-l:3:2xyleno1 (M. P. l03105 C.) 179 161138 Do. Diethylamino-methyl-l13:2-xyleuol (a viscous oil) 162 142 117Do. Dibuty1amino-methyl-1:3:2-xylenol (a viscous oil) 163 145 108 Do.Morpholino methyl-1:3:2-xylenol (a soft resin) 168 Not tested 100 Do.

' will retard that deterioration which rubber normally undergoes throughthe action of heat, light and oxygen. A further object is to incorporatein rubber a class of compounds of the above type which do not stain therubber to a material extent even on exposure to ultraviolet light. Stillfurther objects are to provide new compositions of matter and to advancethe art. Other objects still appear hereinafter.

These objects may be accomplished in accordance with our invention whichcomprises pro- The vulcanized rubber used in the test was made from thefollowing mix, in which the parts are by weight:

. Parts Pale crepe rubber 100 Zinc oxide 10 Blanc fixe '75 Stearic acid1 Sulphur 3 Diphenylguanidine 0.5 Antioxidant 1 The testing was carriedout by subjecting samples of the vulcanizates to artifical ageing for 4days at 70 C. in oxygen at 300 lb./sq. in. pressure,

and then ascertaining the tensile strength of the aged products. Theywere also subjected to ultra- 5 violet light for 8 hours and examinedfor any discoloration.

This is a division of our co-pending application Ser. No. 81,124, filedMay 21, 1936, entitled Preservation of rubber.

19 While we have disclosed the preferred embodiments of our inventionand the preferred modes of carrying the same into efiect, it will bereadily apparent to those skilled in the art that many variations andmodifications may be made there- 15 in without departing from the spiritof our invention. For example, other dialkylamines which may be employedin accordance with our invention are diethylamine, diphopylamine,dibutylamine, methyl ethylamine and their isomers such 20 asdi-isopropylamine, di-isobutylamine and the like. Accordingly, the scopeof our invention is to be limit-ed solely by the appended claimsconstrued as broadly as is permissible in View of the prior art.

We claim:

1. The method of preserving rubber which comprises incorporating thereina 1:3:2-xylenol substituted in the 5-position by a methyl group havingone hydrogen replaced by an amino radi- 30 cal, in which the aminoradical is a member of the group consisting of piperidino, morpholinoand dialkylamino radicals, each alkyl group containing 1 to 4 carbonatoms.

2. The method of preserving rubber which comprises incorporating thereina 5-dialkylaminomethyl 1:3:2-xy1enol, in which each alkyl group contains1 to 4 carbon atoms.

3. The method of preserving rubber which comprises incorporating therein5-dimethylaminoethyl 1 :3 :2-xylenol.'

4. The method of preserving rubber which comprises incorporating therein5-piperidinomethyl 1 3 2-xylenol.

5. Rubber having incorporated therein a 1:3:2-

xylenol substituted in the 5-position by a methyl group having onehydrogen replaced by an amino radical, in which the amino radical is amember of the group consisting of piperidino, morpholino anddialkylamino radicals, each alkyl group containing 1 to 4 carbon atoms.

6. Rubber having incorporated therein a 5- dialkylaminomethyl1:3:2-xylenol, in which each alkyl group contains 1 to 4 carbon atoms.

7. Rubber having incorporated therein 5-dimethylaminomethyl 1 32-xylenol.

8. Rubber having incorporated therein 5-piperidinomethyl 1:3:2-xyleno-l.

ILLIAM BAIRD. MALDWYN JONES.

CERTIFICATE OF CORRECTION.

Patent No. 2,1 1,719. November 2 1.9 9.

WILLIAM BAIRD, ET AL. It is hereby certified that error appears in theprinted specification of the above numbered patent requiring correctionas follows: Page 2, first columnrline 18, for "diphopylamine readdipr'opylamin'e; and second column, line 10, claim 5, for "ethyl" readmethyl; and that the said Letters Patent should be read with thiscorrection therein that the same may conform to the record of the casein the Patent Office.

Signed and sealed this 2nd day of January, A.. D. l9l O.

Henry Van Arsdale,

(Seal) Acting Commissioner of Patents.

